I would like somebody a bit more seasoned with filters than I to clear up some confusion I have been having. I decided recently that a more a cost effective way to dabble with some macro photography and/or increase my focal length capabilities would be to purchase a macro filter or set of filters.

Then came the diopter rating attached to each individual filter. These came in plus +1 +2 +4 +7 +10 etc.

They confused me. I think I've managed to fathom what they are about and this is the conclusion I have drawn.
focal length of the macro filter = 1000 divided by the diopter rating

This would be for example:

1000/+4 = 250mm

which would then give me 305mm focal length? (my current lens is a 18-55mm kit).
which is a zoom from 3x increased 16x

Is that right?

Also, is it true that the lowest + numbers give the highest focal length or is that my imagination?

I might be able to answer that in a few days. I would have to call a friend of mine that used those kind of filters to do her photo work, she could not afford a marco lens for it. Niether could i right now, so i'm thinking the same as you are.

Okay she could not tell me what the +1 or +4 means directly, but I am sure someone in this forum knows.

Macro Filters may be cheap, but she said you have to manual focus with them and most of your camera options are lost when you have those type of lenses mounted. She thought she focused right with her Cam, but when she got the pics onto th ePC they werent totally in focus.

Since you get a set of diffrent rings, I am sure you will find out quick enough. Just remember the losses you get using them.

DO you want to use them for a short time or long time? For long time I myself would go get a Macro Lens.